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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 959

Last Page: 959

Title: Sedimentology of Brent Formation (Middle Jurassic), Statfjord Field, Norway-United Kingdom : ABSTRACT

Author(s): R. J. Moiola, E. L. Jones

Article Type: Meeting abstract


The Brent Formation of Middle Jurassic (Bajocian-Bathonian) age is the primary reservoir in the 3-billion bbl Statfjord field which is located in the northern North Sea on the boundary between Norway and the United Kingdom. Averaging approximately 180 m in thickness, the Brent can be conveniently divided into three major units that are easily identifiable on electric logs. The lower unit is a coarsening-upward sequence that commences with shale and terminates with coarse-grained sandstone. Sandstones in this unit, with porosities as high as 33%, comprise the best part of the reservoir. Interbedded shales, sandstones, siltstones, and coals characterize the middle unit, and the upper unit consists of sandstones with minor thin shales and occasional coals.

Analysis of cores from 10 wells in the field and several wells in nearby areas indicates that the Brent Formation represents a lobate, river-dominated deltaic complex morphologically similar to the Lafource delta of the Mississippi River. The lower unit, in ascending order, consists of prodelta, distal bar, distributary mouth bar, and distributary channel deposits; the heterogeneous middle unit comprises a delta plain association of distributary channel, interdistributary bay, splay, and marsh deposits. The upper unit was also deposited in a delta plain setting, but in places exhibits evidence of marine reworking. Facies patterns and trends demonstrate that the deltaic sediments of the Brent Formation in the Statfjord area were derived from a source area to the south-southeast rather han from the East Shetlands Platform to the west.

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